NEW YORK (CNN) -- While companies across the country are downsizing, some in the fashion world have decided that it's time for a bit of upsizing. This spring, the cheap chic emporiums, Target and Forever 21, will launch plus-size lines for teenagers.

Target's new line of plus-size clothing will go up to size 30. Forever 21's will go up to 2XL.

Forever 21's line, Faith 21, will have sizes ranging from XL-2X, while Target's Pure Energy line will go up to a size 30.

It's about time, said several shoppers scouring the crowded racks of a Forever 21 branch in downtown Manhattan, New York, one recent afternoon.

"I would love to be able to shop in one store with my friends that are all different sizes," said one young petite college student, who was eyeing the $2.50 tank tops. "I think it's great that they're expanding."

Another shopper, a full-figured teen in a stylish baby doll dress, was also excited. "I tried on something earlier that was totally cute and it did not fit my breast size, which is really frustrating, because I liked it." Watch two reactions to the new lines »

"In the past we've had XL sizes and we would sell out of them so quickly," said Heidi Canalizo, a regional manager at Forever 21. "Our customers have been asking for this for so long and in the past few years we've really decided it's time to get into it. Not everyone is a size 2."

Apparently not. In the last 20 years, the rate of obesity among adolescents age 12-19 has more than tripled, increasing from 5 percent to 17.6 percent, according to a National Health and Nutrition Examination survey. Catering to bigger teens could potentially mean bigger bucks for the fashion industry, which has been adversely affected by the recession.

"You're looking at an under $2 billion business that could easily grow to a $4 billion, $5 billion business within a relatively short period of time, like within a year or two," said Marshal Cohen, an analyst for the NPD Group, which studies the clothing market.

"Not only are the [fashion companies] leaving money on the table, they're not even looking at the table. It is a huge opportunity."

Historically, there has been a stigma attached to plus-size clothing, experts said. Many designers don't produce beyond a size 10, even though the average women is a size 14.

"These brands don't want the consumer to aspire to be a plus-size," Cohen said, "they want them to aspire to be that mini-consumer, that slim model that walks down the runway, that's a size 0."

But curvy girls want to be trendy too, said Emme, a popular plus-size super model.

"If you're squishing yourself into clothes that are a couple sizes too small or you're wearing men's clothes, how are you going to go out on a date? How are you going to go to parties with your friends and feel like you fit in? That all has to do with self-esteem and body image," she said.

"Could you imagine taking away all of the clothes for thinner women and saying, 'Sorry, you're too thin. You can't have that.' It doesn't make sense."

Not all are pleased with the supersizing of teen clothing.

"Yeah, as capitalists they have the right to address a growing marketplace and it's a smart business decision," said MeMe Roth, president of the organization National Action Against Obesity.

"However, when you look at the human cost, what we're doing is we're on the Titanic and rather than forcing our children into the lifeboat, we're telling them to join the band. Worrying about fashion rather than worrying about the food is a horrible message that we're sending these kids," Roth said.

The critics have got it all wrong, said Emme.

"I completely disagree that these lines are promoting obesity," she said. "You need to wear clothes to look cool at school. You need to wear clothes to be present in life. And when everybody else has fashion, you should, too."